Camshaft question

[Drive35]

Hi all.
I've found many posts on here and jag-lovers about the various camshafts and have seen the Georgiajag guide, which explains the differences, however my 1970 4.2 'original' engine has a 4-hole cam on the exhaust side with the groove around the flange (haven't checked the other side yet), which doesn't feature in the options!
I note the sprocket only has 2 holes and apparently a bodge with the wired bolts? Don't know if the cylinder head has been replaced at some time.

I'm in the process of fitting tappet guide hold-down plates, but am confused by the camshaft info. The tappet clearances are all about .006", which doesn't appear to be correct for my car (.012-014"), however it runs OK (apart from noisy tappet guides) and did 250 miles last weekend to Bicester.
Should I be concerned
Geoff

[mystery type]

Bolts with locking wires look good to me Geoff.

[mgcjag]

Hi Geoff.....as above wireing looks ok...iv seen it done like this on several cars...re the gaps. ...i would re measure..it would be very unusual if the gaps were all the same......however your cams are the later type so should be 12&14....... when i first got my E some had no gaps at all.....the inlet cam should look the same as your exhaust......why are you fitting hold downs. ....do you nave a problem. ......whilst in there check the drive sprockets as mentioned on Georgia Jag.....if they are the scoloped type then replace them.....Steve

[Drive35]

Thanks Steve
Needed to fit the hold-down plates as the tappet guides were lifting - at least 3 of them have been touching the cam lobes! The sprockets appear to be the good ones.
The gaps do vary, but are all between .004 & 006, so I'll have to look into changing the shims.

[abowie]

Geoff you probably don't want to hear this but if you do actually have 3 loose tappet guides you really should take the head off and have the whole thing rebuilt. You risk major engine damage otherwise.

The hold downs are not there to fix a loose guide, but rather to prevent a guide coming loose in the first place.

I know that there was a vocal proponent of installing hold downs with the head in situ on JL recently, but if he did fit one set of guides on his car and got away with it he was lucky.

I've fitted a lot of sets of these hold downs and it should be done with the head off.

Firstly because you can't drill and tap the holes without getting swarf all through your engine.

Secondly because the hold down can actually distort the tappet guide, leading to the bucket jamming in the bore. You need to be able to check that the bucket slides in and out easily once you've tightened it all down. Early kits came with self tapping screws and these were a lot more likely to cause this problem. Use proper Allen head setscrews and make sure you tap the holes well for an easy fit.

Additionally because your guides are loose and moving in the head there's no guarantee that the hold down will anchor the guide straight either, risking the same problem.

Take the head off. Get all the guides checked and have any loose ones replaced. Then fit your hold downs. If you currently have tappet noise have long skirt 1.4" diameter oversized tappets fitted. Get all your valve guides checked, K Lined and fitted with new stem seals where appropriate. Do anything else that the machinist thinks you should.

With the head off you can measure your cams and determine what they are and then you can shim them appropriately for whatever profile you have.

It'll cost you a grand and take a month, but you'll end up with a perfect head and avoid damage to your engine.

Cheers

[mgcjag]

Good advice above from Andrew.......

[abowie]

Good advice above from Andrew.......

Lol. I do my best...

[Robsan]

I keep looking at that camshaft sprocket bolt head saftey wiring, and should say it doesnt seem right for me. In the mid seventies I worked for a while at Roder in Germany on aircraft electrics, so became familier with safety wire locking of bolts. I accept that the E type is not an aircraft, nevertheless the safety wire locking principle still apply, particularly in high rotational velocity settings such as this application

http://roederaero.de/en/

In the OP photo there is a sloppy bit of wire, and although it is on the "slack side" of the bolt head, you should never have sloppy bits of wire anywhere in the safety wiring configuration. The following images may help for configuration possibilities

https://www.google.com/search?q=how+to+ ... 2&dpr=1.25

hope this helps

[Drive35]

Thanks Andrew for the comprehensive info there and Robsan for the wiring link.
I did go ahead and fit the plates yesterday. Having read all the various posts, including some of yours Andrew, I decided to drill very carefully to just get enough depth for the screw length, without breaking through into the oil chamber, and of course was very careful to mask everything and collect all the swarf. The kit was bought from SNGB, after talking to their tech guy last week, but disappointingly came with hex-head screws.

I appreciate the point about possible distortion of the guides and I will be checking everything moves OK and, maybe again after warming up the engine.
Will be looking at who can do the head work in due course.

[chrisfell]

“....locking wires look good .....”.

Nope, not to me. I agree with Robsan.

As shown in that photo the wire doesn’t lock. When two bolts heads are locked together they must be wired with a double twisted strand in a Z shape.